Zoom lens system, imaging device and camera

ABSTRACT

A zoom lens system comprising a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, a fourth lens unit having negative optical power, and a fifth lens unit having positive optical power, wherein the third lens unit includes at least one lens element having positive optical power and at least one lens element having negative optical power, at least the first to third lens units are moved along an optical axis in zooming so that air spaces between the respective lens units vary, thereby performing magnification change, a lens unit positioned on the image side relative to an aperture diaphragm is moved along the optical axis in focusing, and the conditions: 8.1&lt;f G1 /Ir&lt;10.4 and Z=f T /f W ≧9.0 (f G1 : a composite focal length of the first lens unit, Ir=f T ×tan (ω T ), ω T : a half view angle at a telephoto limit, f T  and f W : focal lengths of the entire system at a telephoto limit and at a wide-angle limit) are satisfied; an imaging device; and a camera are provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on application No. 2010-102639 filed in Japanon Apr. 27, 2010, the contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens system, an imaging device,and a camera. In particular, the present invention relates to: a zoomlens system which is compact but has a wide view angle at a wide-anglelimit and a high zooming ratio, and still is able to perform rapidfocusing and has high optical performance particularly in a close-objectin-focus condition; an imaging device employing the zoom lens system;and a thin and compact camera employing the imaging device.

2. Description of the Background Art

Size reduction and high performance, particularly, a high zooming ratio,are strongly required of cameras having image sensors performingphotoelectric conversion, such as digital still cameras and digitalvideo cameras (simply referred to as digital cameras, hereinafter). Inrecent years, high-speed focusing and high optical performance in aclose-object in-focus condition are increasingly required.

As examples of such zoom lens system having a high zooming ratio, therehave conventionally been proposed various kinds of zoom lens systems andimaging optical systems, each having a five-unit configuration ofpositive, negative, positive, negative, and positive, in which, forexample, a first lens unit having positive optical power, a second lensunit having negative optical power, a third lens unit having positiveoptical power, a fourth lens unit having negative optical power, and afifth lens unit having positive optical power are arranged in order fromthe object side to the image side.

Japanese Laid-Open Patent Publication No. 2007-279587 discloses a zoomlens having the five-unit configuration of positive, negative, positive,negative, and positive, in which air spaces between the respective lensunits, the first to fifth lens units, are varied to performmagnification change, the interval between the first and second lensunits is increased while the interval between the second and third lensunits is reduced at a telephoto limit relative to a wide-angle limit,the first lens unit comprises a lens element, the second lens unitincludes a positive lens and a negative lens, and the total number oflenses in the first and second lens units is four or less.

Japanese Laid-Open Patent Publication No. 2009-282398 discloses a zoomlens having the five-unit configuration of positive, negative, positive,negative, and positive, in which, in zooming from a wide-angle limit toa telephoto limit, all the lens units are moved so that the intervalbetween the first and second lens units is increased and the intervalbetween the third and fifth lens units is increased, and therelationships among the focal length of the fourth lens unit, the focallength of the fifth lens unit, the focal length of the entire system ata wide-angle limit, and the focal length of the entire system at atelephoto limit are set forth.

Japanese Laid-Open Patent Publication No. 2009-163066 discloses a zoomlens having the five-unit configuration of positive, negative, positive,negative, and positive, in which the intervals between the respectivelens units are varied to perform magnification change, the first lensunit comprises a negative lens and at least one positive lens, and therelationship between the refractive index and the Abbe number, to thed-line of the negative lens in the first lens unit, is set forth.

Japanese Laid-Open Patent Publication No. 2009-047785 discloses a zoomlens having the five-unit configuration of positive, negative, positive,negative, and positive, in which, when the lens positions are changedfrom a wide-angle limit to a telephoto limit, at least the second lensunit moves to the image side, the third lens unit moves to the objectside, the fourth lens unit is fixed in the optical axis direction, anaperture diaphragm is arranged close to the object side of the thirdlens unit, the relationship between the focal length of the second lensunit and the focal length of the fourth lens unit is set forth, and therelationship between the amount of movement of the third lens unit whenthe lens positions are changed and the focal length of the entire lenssystem at the telephoto limit is set forth.

Japanese Laid-Open Patent Publication No. 2007-264174 discloses animaging optical system having the five-unit configuration of positive,negative, positive, negative, and positive, in which the fourth lensunit is fixed relative to the image surface and the intervals betweenthe respective lens units are varied at the time of magnification changefrom a wide-angle limit to a telephoto limit, the fourth lens unit movesin a direction substantially vertical to the optical axis at the time ofimage blur compensation, the relationship between the focal length ofthe first lens unit and the focal length of the entire system at thewide-angle limit is set forth, and the relationship between the focallength of the fourth lens unit and the focal length of the entire systemat the telephoto limit is set forth.

Japanese Laid-Open Patent Publication No. 2008-304708 discloses a zoomlens having the five-unit configuration of positive, negative, positive,negative, and positive, in which an optical diaphragm is positionedbetween the second lens unit and the fourth lens unit, the fourth lensunit comprises a negative lens having at least one aspheric surface anda paraxial radius of curvature of its image side surface, which issmaller than that of its object side surface, and the relationshipsamong the focal length of the fourth lens unit, the focal length of theentire system at a wide-angle limit, and the focal length of the entiresystem at a telephoto limit are set forth.

The zoom lenses and the imaging optical system, which are disclosed inthe above-described patent literatures, are downsized enough to beapplicable to thin and compact digital cameras, and have a relativelywide view angle at a wide-angle limit or have a high zooming ratio ofabout 9 or more. However, these conventional zoom lenses and imagingoptical system are not sufficient in the focusing speed and the opticalperformance in the close-object in-focus condition, and therefore, donot meet the requirements for digital cameras in recent years.

SUMMARY OF THE INVENTION

An object of the present invention is to provide: a zoom lens systemwhich is compact but has a wide view angle at a wide-angle limit and ahigh zooming ratio, and still is able to perform rapid focusing and hashigh optical performance particularly in a close-object in-focuscondition; an imaging device employing the zoom lens system; and a thinand compact camera employing the imaging device.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the conventional art, and herein is disclosed:

a zoom lens system, in order from an object side to an image side,comprising a first lens unit having positive optical power, a secondlens unit having negative optical power, a third lens unit havingpositive optical power, a fourth lens unit having negative opticalpower, and a fifth lens unit having positive optical power, wherein

the third lens unit includes at least one lens element having positiveoptical power and at least one lens element having negative opticalpower,

in zooming from a wide-angle limit to a telephoto limit at the time ofimage taking, at least the first lens unit, the second lens unit, andthe third lens unit are individually moved along an optical axis so thatair spaces between the respective lens units vary, thereby performingmagnification change,

in focusing from an infinity in-focus condition to a close-objectin-focus condition, a lens unit positioned on the image side relative toan aperture diaphragm is moved along the optical axis, and

the following conditions (1-2) and (a) are satisfied:

8.1<f_(G1)/Ir<10.4  (1-2)

Z=f _(T) /f _(W)≧9.0  (a)

where

f_(G1) is a composite focal length of the first lens unit,

Ir is a value represented by the following equation:

Ir=f _(T)×tan (ω_(T)),

ω_(T) is a half view angle (°) at a telephoto limit,

f_(T) is a focal length of the entire system at a telephoto limit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the conventional art, and herein is disclosed:

an imaging device capable of outputting an optical image of an object asan electric image signal, comprising:

a zoom lens system that forms an optical image of the object; and

an image sensor that converts the optical image formed by the zoom lenssystem into the electric image signal, wherein

the zoom lens system, in order from an object side to an image side,comprises a first lens unit having positive optical power, a second lensunit having negative optical power, a third lens unit having positiveoptical power, a fourth lens unit having negative optical power, and afifth lens unit having positive optical power, in which

the third lens unit includes at least one lens element having positiveoptical power and at least one lens element having negative opticalpower,

in zooming from a wide-angle limit to a telephoto limit at the time ofimage taking, at least the first lens unit, the second lens unit, andthe third lens unit are individually moved along an optical axis so thatair spaces between the respective lens units vary, thereby performingmagnification change,

in focusing from an infinity in-focus condition to a close-objectin-focus condition, a lens unit positioned on the image side relative toan aperture diaphragm is moved along the optical axis, and

the following conditions (1-2) and (a) are satisfied:

8.1<f_(G1)/Ir<10.4  (1-2)

Z=f _(T) /f _(W)≧9.0  (a)

where

f_(G1) is a composite focal length of the first lens unit,

Ir is a value represented by the following equation:

Ir=f_(T)×tan (ω_(T)),

ω_(T) is a half view angle (°) at a telephoto limit,

f_(T) is a focal length of the entire system at a telephoto limit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the conventional art, and herein is disclosed:

a camera for converting an optical image of an object into an electricimage signal and then performing at least one of displaying and storingof the converted image signal, comprising:

an imaging device including a zoom lens system that forms the opticalimage of the object and an image sensor that converts the optical imageformed by the zoom lens system into the electric image signal, wherein

the zoom lens system, in order from an object side to an image side,comprises a first lens unit having positive optical power, a second lensunit having negative optical power, a third lens unit having positiveoptical power, a fourth lens unit having negative optical power, and afifth lens unit having positive optical power, in which

the third lens unit includes at least one lens element having positiveoptical power and at least one lens element having negative opticalpower,

in zooming from a wide-angle limit to a telephoto limit at the time ofimage taking, at least the first lens unit, the second lens unit, andthe third lens unit are individually moved along an optical axis so thatair spaces between the respective lens units vary, thereby performingmagnification change,

in focusing from an infinity in-focus condition to a close-objectin-focus condition, a lens unit positioned on the image side relative toan aperture diaphragm is moved along the optical axis, and

-   -   the following conditions (1-2) and (a) are satisfied:

8.1<f_(G1)/Ir<10.4  (1-2)

Z=f _(T) /f _(W)≧9.0  (a)

where

f_(G1) is a composite focal length of the first lens unit,

Ir is a value represented by the following equation:

Ir=f _(T)×tan (ω_(T)),

ω_(T) is a half view angle (°) at a telephoto limit,

f_(T) is a focal length of the entire system at a telephoto limit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

According to the present invention, it is possible to provide: a zoomlens system which is compact but has a wide view angle at a wide-anglelimit and a high zooming ratio, and still is able to perform rapidfocusing and has high optical performance particularly in a close-objectin-focus condition; an imaging device employing the zoom lens system;and a thin and compact camera employing the imaging device.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other objects and features of this invention will become clearfrom the following description, taken in conjunction with the preferredembodiments with reference to the accompanied drawings in which:

FIG. 1 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 1 (Example 1);

FIG. 2 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Example 1;

FIG. 3 is a lateral aberration diagram of a zoom lens system accordingto Example 1 at a telephoto limit in a basic state where image blurcompensation is not performed and in a blur compensation state;

FIG. 4 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 2 (Example 2);

FIG. 5 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Example 2;

FIG. 6 is a lateral aberration diagram of a zoom lens system accordingto Example 2 at a telephoto limit in a basic state where image blurcompensation is not performed and in a blur compensation state;

FIG. 7 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 3 (Example 3);

FIG. 8 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Example 3;

FIG. 9 is a lateral aberration diagram of a zoom lens system accordingto Example 3 at a telephoto limit in a basic state where image blurcompensation is not performed and in a blur compensation state;

FIG. 10 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 4 (Example 4);

FIG. 11 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Example 4;

FIG. 12 is a lateral aberration diagram of a zoom lens system accordingto Example 4 at a telephoto limit in a basic state where image blurcompensation is not performed and in a blur compensation state;

FIG. 13 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 5 (Example 5);

FIG. 14 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Example 5;

FIG. 15 is a lateral aberration diagram of a zoom lens system accordingto Example 5 at a telephoto limit in a basic state where image blurcompensation is not performed and in a blur compensation state;

FIG. 16 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 6 (Example 6);

FIG. 17 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Example 6;

FIG. 18 is a lateral aberration diagram of a zoom lens system accordingto Example 6 at a telephoto limit in a basic state where image blurcompensation is not performed and in a blur compensation state; and

FIG. 19 is a schematic construction diagram of a digital still cameraaccording to Embodiment 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 6

FIGS. 1, 4, 7, 10, 13, and 16 are lens arrangement diagrams of zoom lenssystems according to Embodiments 1 to 6, respectively.

Each of FIGS. 1, 4, 7, 10, 13, and 16 shows a zoom lens system in aninfinity in-focus condition. In each Fig., part (a) shows a lensconfiguration at a wide-angle limit (in the minimum focal lengthcondition: focal length f_(w)), part (b) shows a lens configuration at amiddle position (in an intermediate focal length condition: focal lengthf_(M)=√(f_(W)*f_(T))), and part (c) shows a lens configuration at atelephoto limit (in the maximum focal length condition: focal lengthf_(T)). Further, in each Fig., an arrow of straight or curved lineprovided between part (a) and part (b) indicates the movement of eachlens unit from a wide-angle limit through a middle position to atelephoto limit. Moreover, in each Fig., an arrow imparted to a lensunit indicates focusing from an infinity in-focus condition to aclose-object in-focus condition. That is, the arrow indicates the movingdirection at the time of focusing from an infinity in-focus condition toa close-object in-focus condition.

The zoom lens system according to each embodiment, in order from theobject side to the image side, comprises: a first lens unit G1 havingpositive optical power; a second lens unit G2 having negative opticalpower; a third lens unit G3 having positive optical power; a fourth lensunit G4 having negative optical power; and a fifth lens unit G5 havingpositive optical power. In zooming, at least the first lens unit G1, thesecond lens unit G2, and the third lens unit G3 move in a directionalong the optical axis so that the intervals between the respective lensunits, that is, the interval between the first lens unit G1 and thesecond lens unit G2, the interval between the second lens unit G2 andthe third lens unit G3, the interval between the third lens unit G3 andthe fourth lens unit G4, and the interval between the fourth lens unitG4 and the fifth lens unit G5, should all vary. In the zoom lens systemaccording to each embodiment, since these lens units are arranged in thedesired optical power configuration, size reduction in the entire lenssystem is achieved while maintaining high optical performance.

In FIGS. 1, 4, 7, 10, 13, and 16, an asterisk “*” imparted to aparticular surface indicates that the surface is aspheric. In each Fig.,symbol (+) or (−) imparted to the symbol of each lens unit correspondsto the sign of the optical power of the lens unit. In each Fig., thestraight line located on the most right-hand side indicates the positionof the image surface S. On the object side relative to the image surfaceS (that is, between the image surface S and the most image side lenssurface of the fifth lens unit G5), a plane parallel plate P equivalentto an optical low-pass filter or a face plate of an image sensor isprovided.

Further, as shown in FIGS. 1, 4, 7, 10, 13, and 16, an aperturediaphragm A is provided between the second lens unit G2 and the thirdlens unit G3.

As shown in FIG. 1, in the zoom lens system according to Embodiment 1,the first lens unit G1, in order from the object side to the image side,comprises: a negative meniscus first lens element L1 with the convexsurface facing the object side; a positive meniscus second lens elementL2 with the convex surface facing the object side; and a positivemeniscus third lens element L3 with the convex surface facing the objectside. Among these, the first lens element L1 and the second lens elementL2 are cemented with each other. In the surface data in thecorresponding numerical example described later, surface number 2indicates a cement layer between the first lens element L1 and thesecond lens element L2.

In the zoom lens system according to Embodiment 1, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus fourth lens element L4 with the convex surface facingthe object side; a bi-concave fifth lens element L5; and a bi-convexsixth lens element L6. Among these, the fourth lens element L4 has twoaspheric surfaces, and the fifth lens element L5 has an aspheric objectside surface.

In the zoom lens system according to Embodiment 1, the third lens unitG3, in order from the object side to the image side, comprises: abi-convex seventh lens element L7; a bi-convex eighth lens element L8;and a bi-concave ninth lens element L9. Among these, the eighth lenselement L8 and the ninth lens element L9 are cemented with each other.In the surface data in the corresponding numerical example describedlater, surface number 17 indicates a cement layer between the eighthlens element L8 and the ninth lens element L9. The seventh lens elementL7 has two aspheric surfaces, and the ninth lens element L9 has anaspheric image side surface.

In the zoom lens system according to Embodiment 1, the fourth lens unitG4 comprises solely a negative meniscus tenth lens element L10 with theconvex surface facing the object side. The tenth lens element L10 has anaspheric object side surface.

In the zoom lens system according to Embodiment 1, the fifth lens unitG5 comprises solely a bi-convex eleventh lens element L11. The eleventhlens element L11 has two aspheric surfaces.

In the zoom lens system according to Embodiment 1, an aperture diaphragmA is provided on the object side relative to the third lens unit G3(between the sixth lens element L6 and the seventh lens element L7), anda plane parallel plate P is provided on the object side relative to theimage surface S (between the image surface S and the eleventh lenselement L11).

In the zoom lens system according to Embodiment 1, in zooming from awide-angle limit to a telephoto limit at the time of image taking, thefirst lens unit G1 and the third lens unit G3 move to the object side,the second lens unit G2 and the fifth lens unit G5 move to the imageside, and the fourth lens unit G4 is fixed relative to the image surfaceS. That is, in zooming, the individual lens units other than the fourthlens unit G4 move along the optical axis so that the interval betweenthe first lens unit G1 and the second lens unit G2 should increase, theinterval between the second lens unit G2 and the third lens unit G3should decrease, the interval between the third lens unit G3 and thefourth lens unit G4 should increase, and the interval between the fourthlens unit G4 and the fifth lens unit G5 should increase. Further, inzooming from a wide-angle limit to a telephoto limit at the time ofimage taking, the aperture diaphragm A moves integrally with the thirdlens unit G3 along the optical axis.

Further, in the zoom lens system according to Embodiment 1, in focusingfrom an infinity in-focus condition to a close-object in-focuscondition, the fifth lens unit G5 moves to the object side along theoptical axis.

As shown in FIG. 4, in the zoom lens system according to Embodiment 2,the first lens unit G1, in order from the object side to the image side,comprises: a negative meniscus first lens element L1 with the convexsurface facing the object side; and a bi-convex second lens element L2.The first lens element L1 and the second lens element L2 are cementedwith each other. In the surface data in the corresponding numericalexample described later, surface number 2 indicates a cement layerbetween the first lens element L1 and the second lens element L2. Thesecond lens element L2 has an aspheric image side surface.

In the zoom lens system according to Embodiment 2, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus third lens element L3 with the convex surface facingthe object side; a bi-concave fourth lens element L4; and a positivemeniscus fifth lens element L5 with the convex surface facing the objectside. Among these, the third lens element L3 has two aspheric surfaces,and the fourth lens element L4 has an aspheric object side surface.

In the zoom lens system according to Embodiment 2, the third lens unitG3, in order from the object side to the image side, comprises: abi-convex sixth lens element L6; a bi-convex seventh lens element L7;and a bi-concave eighth lens element L8. Among these, the seventh lenselement L7 and the eighth lens element L8 are cemented with each other.In the surface data in the corresponding numerical example describedlater, surface number 15 indicates a cement layer between the seventhlens element L7 and the eighth lens element L8. The sixth lens elementL6 has two aspheric surfaces, and the eighth lens element L8 has anaspheric image side surface.

In the zoom lens system according to Embodiment 2, the fourth lens unitG4 comprises solely a negative meniscus ninth lens element L9 with theconvex surface facing the object side. The ninth lens element L9 has anaspheric object side surface.

In the zoom lens system according to Embodiment 2, the fifth lens unitG5 comprises solely a bi-convex tenth lens element L10. The tenth lenselement L10 has two aspheric surfaces.

In the zoom lens system according to Embodiment 2, an aperture diaphragmA is provided on the object side relative to the third lens unit G3(between the fifth lens element L5 and the sixth lens element L6), and aplane parallel plate P is provided on the object side relative to theimage surface S (between the image surface S and the tenth lens elementL10).

In the zoom lens system according to Embodiment 2, in zooming from awide-angle limit to a telephoto limit at the time of image taking, thefirst lens unit G1 and the third lens unit G3 move to the object side,the second lens unit G2 and the fifth lens unit G5 move to the imageside, and the fourth lens unit G4 is fixed relative to the image surfaceS. That is, in zooming, the individual lens units other than the fourthlens unit G4 move along the optical axis so that the interval betweenthe first lens unit G1 and the second lens unit G2 should increase, theinterval between the second lens unit G2 and the third lens unit G3should decrease, the interval between the third lens unit G3 and thefourth lens unit G4 should increase, and the interval between the fourthlens unit G4 and the fifth lens unit G5 should increase. Further, inzooming from a wide-angle limit to a telephoto limit at the time ofimage taking, the aperture diaphragm A moves integrally with the thirdlens unit G3 along the optical axis.

Further, in the zoom lens system according to Embodiment 2, in focusingfrom an infinity in-focus condition to a close-object in-focuscondition, the fifth lens unit G5 moves to the object side along theoptical axis.

As shown in FIG. 7, in the zoom lens system according to Embodiment 3,the first lens unit G1, in order from the object side to the image side,comprises: a negative meniscus first lens element L1 with the convexsurface facing the object side; a bi-convex second lens element L2; anda positive meniscus third lens element L3 with the convex surface facingthe object side. Among these, the first lens element L1 and the secondlens element L2 are cemented with each other. In the surface data in thecorresponding numerical example described later, surface number 2indicates a cement layer between the first lens element L1 and thesecond lens element L2.

In the zoom lens system according to Embodiment 3, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus fourth lens element L4 with the convex surface facingthe object side; a bi-concave fifth lens element L5; and a bi-convexsixth lens element L6. Among these, the fourth lens element L4 has twoaspheric surfaces.

In the zoom lens system according to Embodiment 3, the third lens unitG3, in order from the object side to the image side, comprises: abi-convex seventh lens element L7; a positive meniscus eighth lenselement L8 with the convex surface facing the image side; and abi-concave ninth lens element L9. Among these, the eighth lens elementL8 and the ninth lens element L9 are cemented with each other. In thesurface data in the corresponding numerical example described later,surface number 17 indicates a cement layer between the eighth lenselement L8 and the ninth lens element L9. The seventh lens element L7has two aspheric surfaces, and the ninth lens element L9 has an asphericimage side surface.

In the zoom lens system according to Embodiment 3, the fourth lens unitG4 comprises solely a negative meniscus tenth lens element L10 with theconvex surface facing the object side. The tenth lens element L10 has anaspheric image side surface.

In the zoom lens system according to Embodiment 3, the fifth lens unitG5 comprises solely a bi-convex eleventh lens element L11. The eleventhlens element L11 has two aspheric surfaces.

In the zoom lens system according to Embodiment 3, an aperture diaphragmA is provided on the object side relative to the third lens unit G3(between the sixth lens element L6 and the seventh lens element L7), anda plane parallel plate P is provided on the object side relative to theimage surface S (between the image surface S and the eleventh lenselement L11).

In the zoom lens system according to Embodiment 3, in zooming from awide-angle limit to a telephoto limit at the time of image taking, thefirst lens unit G1, the third lens unit G3, and the fourth lens unit G4move to the object side, the second lens unit G2 moves to the imageside, and the fifth lens unit G5 moves with locus of a convex to theobject side so that the position of the fifth lens unit G5 at thetelephoto limit is approximately equal to the position at the wide-anglelimit. That is, in zooming, the individual lens units move along theoptical axis so that the interval between the first lens unit G1 and thesecond lens unit G2 should increase, the interval between the secondlens unit G2 and the third lens unit G3 should decrease, the intervalbetween the third lens unit G3 and the fourth lens unit G4 shouldincrease, and the interval between the fourth lens unit G4 and the fifthlens unit G5 should increase. Further, in zooming from a wide-anglelimit to a telephoto limit at the time of image taking, the aperturediaphragm A moves along the optical axis with the interval between theaperture diaphragm A and the third lens unit G3 being varied.

Further, in the zoom lens system according to Embodiment 3, in focusingfrom an infinity in-focus condition to a close-object in-focuscondition, the fifth lens unit G5 moves to the object side along theoptical axis.

As shown in FIG. 10, in the zoom lens system according to Embodiment 4,the first lens unit G1, in order from the object side to the image side,comprises: a negative meniscus first lens element L1 with the convexsurface facing the object side; a bi-convex second lens element L2; anda positive meniscus third lens element L3 with the convex surface facingthe object side. Among these, the first lens element L1 and the secondlens element L2 are cemented with each other. In the surface data in thecorresponding numerical example described later, surface number 2indicates a cement layer between the first lens element L1 and thesecond lens element L2.

In the zoom lens system according to Embodiment 4, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus fourth lens element L4 with the convex surface facingthe object side; a bi-concave fifth lens element L5; and a bi-convexsixth lens element L6. Among these, the fourth lens element L4 has twoaspheric surfaces.

In the zoom lens system according to Embodiment 4, the third lens unitG3, in order from the object side to the image side, comprises: abi-convex seventh lens element L7; a positive meniscus eighth lenselement L8 with the convex surface facing the image side; and abi-concave ninth lens element L9. Among these, the eighth lens elementL8 and the ninth lens element L9 are cemented with each other. In thesurface data in the corresponding numerical example described later,surface number 17 indicates a cement layer between the eighth lenselement L8 and the ninth lens element L9. The seventh lens element L7has two aspheric surfaces, and the ninth lens element L9 has an asphericimage side surface.

In the zoom lens system according to Embodiment 4, the fourth lens unitG4 comprises solely a negative meniscus tenth lens element L10 with theconvex surface facing the object side. The tenth lens element L10 has anaspheric image side surface.

In the zoom lens system according to Embodiment 4, the fifth lens unitG5 comprises solely a bi-convex eleventh lens element L11. The eleventhlens element L11 has two aspheric surfaces.

In the zoom lens system according to Embodiment 4, an aperture diaphragmA is provided on the object side relative to the third lens unit G3(between the sixth lens element L6 and the seventh lens element L7), anda plane parallel plate P is provided on the object side relative to theimage surface S (between the image surface S and the eleventh lenselement L11).

In the zoom lens system according to Embodiment 4, in zooming from awide-angle limit to a telephoto limit at the time of image taking, thefirst lens unit G1 and the third lens unit G3 move to the object side,the second lens unit G2 moves with locus of a convex to the image sideso that the position of the second lens unit G2 at the telephoto limitis on the image side relative to the position at the wide-angle limit,the fifth lens unit G5 moves with locus of a convex to the object sideso that the position of the fifth lens unit G5 at the telephoto limit ison the image side relative to the position at the wide-angle limit, andthe fourth lens unit G4 is fixed relative to the image surface S. Thatis, in zooming, the individual lens units other than the fourth lensunit G4 move along the optical axis so that the interval between thefirst lens unit G1 and the second lens unit G2 should increase, theinterval between the second lens unit G2 and the third lens unit G3should decrease, the interval between the third lens unit G3 and thefourth lens unit G4 should increase, and the interval between the fourthlens unit G4 and the fifth lens unit G5 should increase. Further, inzooming from a wide-angle limit to a telephoto limit at the time ofimage taking, the aperture diaphragm A moves integrally with the thirdlens unit G3 along the optical axis.

Further, in the zoom lens system according to Embodiment 4, in focusingfrom an infinity in-focus condition to a close-object in-focuscondition, the fifth lens unit G5 moves to the object side along theoptical axis.

As shown in FIG. 13, in the zoom lens system according to Embodiment 5,the first lens unit G1, in order from the object side to the image side,comprises: a negative meniscus first lens element L1 with the convexsurface facing the object side; a bi-convex second lens element L2; anda positive meniscus third lens element L3 with the convex surface facingthe object side. Among these, the first lens element L1 and the secondlens element L2 are cemented with each other. In the surface data in thecorresponding numerical example described later, surface number 2indicates a cement layer between the first lens element L1 and thesecond lens element L2.

In the zoom lens system according to Embodiment 5, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus fourth lens element L4 with the convex surface facingthe object side; a negative meniscus fifth lens element L5 with theconvex surface facing the image side; and a bi-convex sixth lens elementL6. Among these, the fourth lens element L4 has two aspheric surfaces.

In the zoom lens system according to Embodiment 5, the third lens unitG3, in order from the object side to the image side, comprises: abi-convex seventh lens element L7; a bi-convex eighth lens element L8;and a bi-concave ninth lens element L9. Among these, the eighth lenselement L8 and the ninth lens element L9 are cemented with each other.In the surface data in the corresponding numerical example describedlater, surface number 17 indicates a cement layer between the eighthlens element L8 and the ninth lens element L9. The seventh lens elementL7 has an aspheric object side surface, and the ninth lens element L9has an aspheric image side surface.

In the zoom lens system according to Embodiment 5, the fourth lens unitG4 comprises solely a negative meniscus tenth lens element L10 with theconvex surface facing the object side. The tenth lens element L10 has anaspheric image side surface.

In the zoom lens system according to Embodiment 5, the fifth lens unitG5 comprises solely a positive meniscus eleventh lens element L11 withthe convex surface facing the object side. The eleventh lens element L11has two aspheric surfaces.

In the zoom lens system according to Embodiment 5, an aperture diaphragmA is provided on the object side relative to the third lens unit G3(between the sixth lens element L6 and the seventh lens element L7), anda plane parallel plate P is provided on the object side relative to theimage surface S (between the image surface S and the eleventh lenselement L11).

In the zoom lens system according to Embodiment 5, in zooming from awide-angle limit to a telephoto limit at the time of image taking, thefirst lens unit G1 and the third lens unit G3 move to the object side,the second lens unit G2 moves with locus of a convex to the image sideso that the position of the second lens unit G2 at the telephoto limitis on the image side relative to the position at the wide-angle limit,the fourth lens unit G4 moves with locus of a convex to the image sideso that the position of the fourth lens unit G4 at the telephoto limitis on the object side relative to the position at the wide-angle limit,and the fifth lens unit G5 is fixed relative to the image surface S.That is, in zooming, the individual lens units other than the fifth lensunit G5 move along the optical axis so that the interval between thefirst lens unit G1 and the second lens unit G2 should increase, theinterval between the second lens unit G2 and the third lens unit G3should decrease, the interval between the third lens unit G3 and thefourth lens unit G4 should increase, and the interval between the fourthlens unit G4 and the fifth lens unit G5 should increase. Further, inzooming from a wide-angle limit to a telephoto limit at the time ofimage taking, the aperture diaphragm A moves integrally with the thirdlens unit G3 along the optical axis.

Further, in the zoom lens system according to Embodiment 5, in focusingfrom an infinity in-focus condition to a close-object in-focuscondition, the fourth lens unit G4 moves to the image side along theoptical axis.

As shown in FIG. 16, in the zoom lens system according to Embodiment 6,the first lens unit G1, in order from the object side to the image side,comprises: a bi-convex first lens element L1; a negative meniscus secondlens element L2 with the convex surface facing the image side; and apositive meniscus third lens element L3 with the convex surface facingthe object side. Among these, the first lens element L1 and the secondlens element L2 are cemented with each other. In the surface data in thecorresponding numerical example described later, surface number 2indicates a cement layer between the first lens element L1 and thesecond lens element L2.

In the zoom lens system according to Embodiment 6, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus fourth lens element L4 with the convex surface facingthe object side; a negative meniscus fifth lens element L5 with theconvex surface facing the image side; and a bi-convex sixth lens elementL6. Among these, the fourth lens element L4 has two aspheric surfaces.

In the zoom lens system according to Embodiment 6, the third lens unitG3, in order from the object side to the image side, comprises: abi-convex seventh lens element L7; a positive meniscus eighth lenselement L8 with the convex surface facing the image side; and abi-concave ninth lens element L9. Among these, the eighth lens elementL8 and the ninth lens element L9 are cemented with each other. In thesurface data in the corresponding numerical example described later,surface number 17 indicates a cement layer between the eighth lenselement L8 and the ninth lens element L9. The seventh lens element L7has two aspheric surfaces, and the ninth lens element L9 has an asphericimage side surface.

In the zoom lens system according to Embodiment 6, the fourth lens unitG4 comprises solely a negative meniscus tenth lens element L10 with theconvex surface facing the object side. The tenth lens element L10 has anaspheric image side surface.

In the zoom lens system according to Embodiment 6, the fifth lens unitG5 comprises solely a bi-convex eleventh lens element L11. The eleventhlens element L11 has two aspheric surfaces.

In the zoom lens system according to Embodiment 6, an aperture diaphragmA is provided on the object side relative to the third lens unit G3(between the sixth lens element L6 and the seventh lens element L7), anda plane parallel plate P is provided on the object side relative to theimage surface S (between the image surface S and the eleventh lenselement L11).

In the zoom lens system according to Embodiment 6, in zooming from awide-angle limit to a telephoto limit at the time of image taking, thefirst lens unit G1 and the third lens unit G3 move to the object side,the second lens unit G2 moves with locus of a convex to the image sideso that the position of the second lens unit G2 at the telephoto limitis on the image side relative to the position at the wide-angle limit,the fifth lens unit G5 moves with locus of a convex to the object sideso that the position of the fifth lens unit G5 at the telephoto limit ison the image side relative to the position at the wide-angle limit, andthe fourth lens unit G4 is fixed relative to the image surface S. Thatis, in zooming, the individual lens units other than the fourth lensunit G4 move along the optical axis so that the interval between thefirst lens unit G1 and the second lens unit G2 should increase, theinterval between the second lens unit G2 and the third lens unit G3should decrease, the interval between the third lens unit G3 and thefourth lens unit G4 should increase, and the interval between the fourthlens unit G4 and the fifth lens unit G5 should increase. Further, inzooming from a wide-angle limit to a telephoto limit at the time ofimage taking, the aperture diaphragm A moves integrally with the thirdlens unit G3 along the optical axis.

Further, in the zoom lens system according to Embodiment 6, in focusingfrom an infinity in-focus condition to a close-object in-focuscondition, the fifth lens unit G5 moves to the object side along theoptical axis.

In the zoom lens systems according to Embodiments 1 to 6, the third lensunit G3 includes at least one lens element having positive optical powerand at least one lens element having negative optical power. Therefore,spherical aberration, coma aberration, and chromatic aberration can befavorably compensated.

In the zoom lens systems according to Embodiments 1 to 6, the fourthlens unit G4 is composed of one lens element, and the fifth lens unit G5is also composed of one lens element. Therefore, the overall length oflens system is short.

In the zoom lens systems according to Embodiments 1 to 6, in focusingfrom an infinity in-focus condition to a close-object in-focuscondition, the fourth lens unit G4 or the fifth lens unit G5, which iscomposed of one lens element and is positioned on the image siderelative to the aperture diaphragm A, moves along the optical axis.Therefore, rapid focusing is easily achieved, and high opticalperformance is obtained particularly in the close-object in-focuscondition. In addition, since the single lens element that moves alongthe optical axis in focusing has an aspheric surface, off-axialcurvature of field from a wide-angle limit to a telephoto limit can befavorably compensated.

Particularly in the zoom lens system according to Embodiment 5, infocusing from an infinity in-focus condition to a close-object in-focuscondition, the fourth lens unit G4 moves along the optical axis.Therefore, the amount of movement of the fourth lens unit G4 in focusingis reduced, which allows a lens barrel to be constructed compactly.

In the zoom lens systems according to Embodiments 1 to 6, in zoomingfrom a wide-angle limit to a telephoto limit at the time of imagetaking, at least the first lens unit G1, the second lens unit G2, andthe third lens unit G3, among the first lens unit G1 to the fifth lensunit G5, are individually moved along the optical axis so that zoomingis achieved. Then, any lens unit among the first lens unit G1 to thefifth lens unit G5, or alternatively a sub lens unit consisting of apart of a lens unit is moved in a direction perpendicular to the opticalaxis, so that image point movement caused by vibration of the entiresystem is compensated, that is, image blur caused by hand blurring,vibration and the like can be compensated optically.

When image point movement caused by vibration of the entire system is tobe compensated, for example, the third lens unit G3 is moved in adirection perpendicular to the optical axis. Thus, compensation of imageblur can be performed in a state that size increase in the entire zoomlens system is suppressed and thereby a compact construction is realizedand that excellent imaging characteristics such as small decenteringcoma aberration and small decentering astigmatism are maintained.

Here, in a case that a lens unit is composed of a plurality of lenselements, the above-mentioned sub lens unit consisting of a part of alens unit indicates any one lens element or alternatively a plurality ofadjacent lens elements among the plurality of lens elements.

The following description is given for conditions preferred to besatisfied by a zoom lens system like the zoom lens systems according toEmbodiments 1 to 6. Here, a plurality of preferable conditions are setforth for the zoom lens system according to each embodiment. Aconstruction that satisfies all the plural conditions is most desirablefor the zoom lens system. However, when an individual condition issatisfied, a zoom lens system having the corresponding effect isobtained.

In a zoom lens system like the zoom lens systems according toEmbodiments 1 to 6, which comprises, in order from the object side tothe image side, a first lens unit having positive optical power, asecond lens unit having negative optical power, a third lens unit havingpositive optical power, a fourth lens unit having negative opticalpower, and a fifth lens unit having positive optical power, in which thethird lens unit includes at least one lens element having positiveoptical power and at least one lens element having negative opticalpower; in zooming from a wide-angle limit to a telephoto limit at thetime of image taking, at least the first lens unit, the second lensunit, and the third lens unit are individually moved along the opticalaxis so that the air spaces between the respective lens units vary,thereby performing magnification change; and in focusing from aninfinity in-focus condition to a close-object in-focus condition, thelens unit positioned on the image side relative to the aperturediaphragm is moved along the optical axis (this lens configuration isreferred to as a basic configuration of the embodiment, hereinafter),the following conditions (1-2) and (a) are satisfied.

8.1<f_(G1)/Ir<10.4  (1-2)

Z=f _(T) /f _(W)≧9.0  (a)

where

f_(G1) is a composite focal length of the first lens unit,

Ir is a value represented by the following equation:

Ir=f _(T)×tan (ω_(T)),

ω_(T) is a half view angle (°) at a telephoto limit,

f_(T) is a focal length of the entire system at a telephoto limit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (1-2) sets forth the relationship between the focal lengthof the first lens unit and the maximum image height. When the value goesbelow the lower limit of the condition (1-2), the refractive power ofthe first lens unit is increased, which makes it difficult to compensatecurvature of field that occurs in the first lens unit. Conversely, whenthe value exceeds the upper limit of the condition (1-2), the refractivepower of the first lens unit is decreased, and the outer diameter of thefirst lens unit is increased to maintain achieving a wider angle, whichmakes it difficult to ensure compactness.

When at least one of the following conditions (1-2)′ and (1-2)″ issatisfied, the above-mentioned effect is achieved more successfully.

9.0<f_(G1)/Ir  (1-2)′

f_(G1)/Ir<10.3  (1-2)″

It is preferable that the conditions (1-2), (1-2)′, and (1-2)″ aresatisfied in the following condition (a)′.

Z=f _(T) /f _(W)>9.3  (a)′

In a zoom lens system having the basic configuration like the zoom lenssystems according to Embodiments 1 to 6, it is preferable that thefollowing condition (2) is satisfied.

28.8<(L_(12T)−L_(12W))×f_(G1)/Ir²<70.0  (2)

where

L_(12T) is an interval between the first lens unit and the second lensunit at a telephoto limit,

L_(12W) is an interval between the first lens unit and the second lensunit at a wide-angle limit,

f_(G1) is a composite focal length of the first lens unit,

Ir is a value represented by the following equation:

Ir=f_(T)×tan (ω_(T)),

ω_(T) is a half view angle (°) at a telephoto limit, and

f_(T) is a focal length of the entire system at a telephoto limit.

The condition (2) sets forth the relationship between: the maximum imageheight; and a multiplier of an amount of change in the interval betweenthe first lens unit and the second lens unit in zooming from awide-angle limit to a telephoto limit at the time of image taking, andthe focal length of the first lens unit. When the value goes below thelower limit of the condition (2), the amount of change in the intervalbetween the first lens unit and the second lens unit in zooming becomesexcessively small, which might make it difficult to obtain a highzooming ratio of 9 or more. Conversely, when the value exceeds the upperlimit of the condition (2), the amount of change in the interval betweenthe first lens unit and the second lens unit in zooming becomesexcessively large, which might make it difficult to provide a compactlens barrel, imaging device, or camera. In addition, the focal length ofthe first lens unit is increased and thereby the amount of movement ofthe first lens unit, which is required for ensuring high magnification,becomes excessively large, which might make it difficult to provide acompact lens barrel, imaging device, or camera.

When at least one of the following conditions (2)′ and (2)″ issatisfied, the above-mentioned effect is achieved more successfully.

32.0<(L_(12T)−L_(12T))×f_(G1)/Ir²  (2)′

(L_(12T)−L_(12W))×f_(G1)/Ir²<65.0  (2)″

It is preferable that the conditions (2), (2)′, and (2)″ are satisfiedin the following condition (a)′.

Z=f _(T) /f _(W)>9.3  (a)′

In a zoom lens system having the basic configuration like the zoom lenssystems according to Embodiments 1 to 6, it is preferable that thefollowing condition (3) is satisfied.

1.85<f_(G3)/D_(G3)<4.29  (3)

where

f_(G3) is a composite focal length of the third lens unit, and

D_(G3) is an optical axial thickness of the third lens unit.

The condition (3) sets forth the relationship between the focal lengthof the third lens unit and the optical axial thickness of the third lensunit. When the value goes below the lower limit of the condition (3),the optical axial thickness of the third lens unit becomes excessivelylarge, which might make it difficult to ensure compactness. Conversely,when the value exceeds the upper limit of the condition (3), the focallength of the third lens unit becomes excessively long, which might makeit difficult to maintain function of the third lens unit formagnification change. As a result, it might be difficult to configure azoom lens system having a zooming ratio of 9 or more with the opticalperformance being maintained.

When at least one of the following conditions (3)′ and (3)″ issatisfied, the above-mentioned effect is achieved more successfully.

1.89<f_(G3)/D_(G3)  (3)′

f_(G3)/D_(G3)<3.8  (3)″

It is preferable that the conditions (3), (3)′, and (3)″ are satisfiedin the following condition (a)′.

Z=f _(T) /f _(W)≧9.3  (a)′

In a zoom lens system having the basic configuration like the zoom lenssystems according to Embodiments 1 to 6, it is preferable that thefollowing condition (4) is satisfied.

−4.2<f_(G1)/f_(G4)<−0.5  (4)

where

f_(G1) is a composite focal length of the first lens unit, and

f_(G4) is a composite focal length of the fourth lens unit.

The condition (4) sets forth the ratio of the focal length of the firstlens unit to the focal length of the fourth lens unit. When the valuegoes below the lower limit of the condition (4), the refractive power ofthe fourth lens unit is increased, which might make it difficult tocompensate curvature of field that occurs in the fourth lens unit.Conversely, when the value exceeds the upper limit of the condition (4),the focal length of the fourth lens unit becomes excessively long, whichmight make it difficult to maintain function of the fourth lens unit formagnification change. As a result, it might be difficult to configure azoom lens system having a zooming ratio of 9 more with the opticalperformance being maintained.

When at least one of the following conditions (4)′ and (4)″ issatisfied, the above-mentioned effect is achieved more successfully.

−3.7≦f_(G1)/f_(G4)  (4)′

f_(G1)/f_(G4)<−0.6  (4)″

It is preferable that the conditions (4), (4)′, and (4)″ are satisfiedin the following condition (a)′.

Z=f _(T) /f _(W)>9.3  (a)′

In a zoom lens system having the basic configuration like the zoom lenssystems according to Embodiments 1 to 6, it is preferable that thefollowing condition (5) is satisfied.

6.0<f_(G1)/f_(W)<9.4  (5)

where

f_(G1) is a composite focal length of the first lens unit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (5) sets forth an appropriate focal length of the firstlens unit. When the value goes below the lower limit of the condition(5), the view angle at a wide-angle limit becomes excessively narrow,which contradicts the purpose of achieving a wider angle. Conversely,when the value exceeds the upper limit of the condition (5), the viewangle at a wide-angle limit is increased. However, such increase in theview angle causes an increase in the outer diameter of the first lensunit, which might make it difficult to ensure compactness.

When at least one of the following conditions (5)′ and (5)″ issatisfied, the above-mentioned effect is achieved more successfully.

6.7<f_(G1)/f_(W)  (5)′

f_(G1)/f_(W)<8.4  (5)″

It is preferable that the conditions (5), (5)′, and (5)″ are satisfiedin the following condition (a)′.

Z=f _(T) /f _(W)>9.3  (a)′

In a zoom lens system having the basic configuration like the zoom lenssystems according to Embodiments 1 to 6, it is preferable that thefollowing condition (6) is satisfied.

4.3<L_(T)/f_(G3)<7.4  (6)

where

L_(T) is an overall length of lens system at a telephoto limit (adistance from the most object side surface of the first lens unit to theimage surface), and

f_(G3) is a composite focal length of the third lens unit.

The condition (6) sets forth the ratio of the overall length of the zoomlens system at a telephoto limit to the focal length of the third lensunit. When the value goes below the lower limit of the condition (6),the overall length of lens system becomes excessively short relative tothe focal length of the third lens unit, which might make it difficultto ensure image surface characteristics and compensate various kinds ofaberrations such as chromatic aberration.

Conversely, when the value exceeds the upper limit of the condition (6),the overall length at a telephoto limit tends to increase, which mightmake it difficult to achieve a compact zoom lens system.

When at least one of the following conditions (6)′ and (6)″ issatisfied, the above-mentioned effect is achieved more successfully.

4.8 <L_(T)/f_(G3)  (6)′

L_(T)/f_(G3)<7.0  (6)″

It is preferable that the conditions (6), (6)′, and (6)″ are satisfiedin the following condition (a)′.

Z=f _(T) /f _(W)>9.3  (a)′

Each of the lens units constituting the zoom lens system according toany of Embodiments 1 to 6 is composed exclusively of refractive typelens elements that deflect the incident light by refraction (that is,lens elements of a type in which deflection is achieved at the interfacebetween media each having a distinct refractive index). However, thepresent invention is not limited to this. For example, the lens unitsmay employ diffractive type lens elements that deflect the incidentlight by diffraction; refractive-diffractive hybrid type lens elementsthat deflect the incident light by a combination of diffraction andrefraction; or gradient index type lens elements that deflect theincident light by distribution of refractive index in the medium. Inparticular, in refractive-diffractive hybrid type lens elements, when adiffraction structure is formed in the interface between media havingmutually different refractive indices, wavelength dependence in thediffraction efficiency is improved. Thus, such a configuration ispreferable.

Moreover, in each embodiment, a configuration has been described that onthe object side relative to the image surface S (that is, between theimage surface S and the most image side lens surface of the fifth lensunit G5), a plane parallel plate P equivalent to an optical low-passfilter or a face plate of an image sensor is provided. This low-passfilter may be: a birefringent type low-pass filter made of, for example,a crystal whose predetermined crystal orientation is adjusted; or aphase type low-pass filter that achieves required characteristics ofoptical cut-off frequency by diffraction.

Embodiment 7

FIG. 19 is a schematic construction diagram of a digital still cameraaccording to Embodiment 7. In FIG. 19, the digital still cameracomprises: an imaging device having a zoom lens system 1 and an imagesensor 2 composed of a CCD; a liquid crystal display monitor 3; and abody 4. The employed zoom lens system 1 is a zoom lens system accordingto Embodiment 1. In FIG. 19, the zoom lens system 1 comprises a firstlens unit G1, a second lens unit G2, an aperture diaphragm A, a thirdlens unit G3, a fourth lens unit G4 and a fifth lens unit G5. In thebody 4, the zoom lens system 1 is arranged on the front side, while theimage sensor 2 is arranged on the rear side of the zoom lens system 1.On the rear side of the body 4, the liquid crystal display monitor 3 isarranged, while an optical image of a photographic object generated bythe zoom lens system 1 is formed on an image surface S.

The lens barrel comprises a main barrel 5, a moving barrel 6 and acylindrical cam 7. When the cylindrical cam 7 is rotated, the first lensunit G1, the second lens unit G2, the aperture diaphragm A and the thirdlens unit G3, the fourth lens unit G4, and the fifth lens unit G5 moveto predetermined positions relative to the image sensor 2, so thatzooming from a wide-angle limit to a telephoto limit is achieved. Thefifth lens unit G5 is movable in an optical axis direction by a motorfor focus adjustment.

As such, when the zoom lens system according to Embodiment 1 is employedin a digital still camera, a small digital still camera is obtained thathas a high resolution and high capability of compensating the curvatureof field and that has a short overall length of lens system at the timeof non-use. Here, in the digital still camera shown in FIG. 19, any oneof the zoom lens systems according to Embodiments 2 to 6 may be employedin place of the zoom lens system according to Embodiment 1. Further, theoptical system of the digital still camera shown in FIG. 19 isapplicable also to a digital video camera for moving images. In thiscase, moving images with high resolution can be acquired in addition tostill images.

Here, the digital still camera according to the present Embodiment 7 hasbeen described for a case that the employed zoom lens system 1 is a zoomlens system according to Embodiments 1 to 6. However, in these zoom lenssystems, the entire zooming range need not be used. That is, inaccordance with a desired zooming range, a range where satisfactoryoptical performance is obtained may exclusively be used. Then, the zoomlens system may be used as one having a lower magnification than thezoom lens system described in Embodiments 1 to 6.

Further, Embodiment 7 has been described for a case that the zoom lenssystem is applied to a lens barrel of so-called barrel retractionconstruction. However, the present invention is not limited to this. Forexample, the zoom lens system may be applied to a lens barrel ofso-called bending configuration where a prism having an internalreflective surface or a front surface reflective mirror is arranged atan arbitrary position within the first lens unit G1 or the like.Further, in Embodiment 7, the zoom lens system may be applied to aso-called sliding lens barrel in which a part of the lens unitsconstituting the zoom lens system like the entirety of the second lensunit G2, the entirety of the third lens unit G3, or alternatively a partof the second lens unit G2 or the third lens unit G3 is caused to escapefrom the optical axis at the time of barrel refraction.

An imaging device comprising a zoom lens system according to Embodiments1 to 6, and an image sensor such as a CCD or a CMOS may be applied to amobile telephone, a PDA (Personal Digital Assistance), a surveillancecamera in a surveillance system, a Web camera, a vehicle-mounted cameraor the like.

The following description is given for numerical examples in which thezoom lens system according to Embodiments 1 to 6 are implementedpractically. In the numerical examples, the units of the length in thetables are all “mm”, while the units of the view angle are all “°”.Moreover, in the numerical examples, r is the radius of curvature, d isthe axial distance, nd is the refractive index to the d-line, and vd isthe Abbe number to the d-line. In the numerical examples, the surfacesmarked with * are aspheric surfaces, and the aspheric surfaceconfiguration is defined by the following expression.

$Z = {\frac{h^{2}/r}{1 + \sqrt{1 - {\left( {1 + \kappa} \right)\left( {h/r} \right)^{2}}}} + {A\; 4h^{4}} + {A\; 6h^{6}} + {A\; 8\; h^{8}} + {A\; 10h^{10}} + {A\; 12h^{12}} + {A\; 14h^{14}}}$

Here, κ is the conic constant, A4, A6, A8, A10, A12, and A14 are afourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, andfourteenth-order aspherical coefficients, respectively.

FIGS. 2, 5, 8, 11, 14, and 17 are longitudinal aberration diagrams ofthe zoom lens systems according to Embodiments 1 to 6, respectively.

In each longitudinal aberration diagram, part (a) shows the aberrationat a wide-angle limit, part (b) shows the aberration at a middleposition, and part (c) shows the aberration at a telephoto limit. Eachlongitudinal aberration diagram, in order from the left-hand side, showsthe spherical aberration (SA (mm)), the astigmatism (AST (mm)) and thedistortion (DIS (%)). In each spherical aberration diagram, the verticalaxis indicates the F-number (in each Fig., indicated as F), and thesolid line, the short dash line and the long dash line indicate thecharacteristics to the d-line, the F-line and the C-line, respectively.In each astigmatism diagram, the vertical axis indicates the imageheight (in each Fig., indicated as H), and the solid line and the dashline indicate the characteristics to the sagittal plane (in each Fig.,indicated as “s”) and the meridional plane (in each Fig., indicated as“m”), respectively. In each distortion diagram, the vertical axisindicates the image height (in each Fig., indicated as H).

FIGS. 3, 6, 9, 12, 15, and 18 are lateral aberration diagrams of thezoom lens systems at a telephoto limit according to Embodiments 1 to 6,respectively.

In each lateral aberration diagram, the aberration diagrams in the upperthree parts correspond to a basic state where image blur compensation isnot performed at a telephoto limit, while the aberration diagrams in thelower three parts correspond to an image blur compensation state wherethe entire third lens unit G3 is moved by a predetermined amount in adirection perpendicular to the optical axis at a telephoto limit. Amongthe lateral aberration diagrams of a basic state, the upper part showsthe lateral aberration at an image point of 75% of the maximum imageheight, the middle part shows the lateral aberration at the axial imagepoint, and the lower part shows the lateral aberration at an image pointof −75% of the maximum image height. Among the lateral aberrationdiagrams of an image blur compensation state, the upper part shows thelateral aberration at an image point of 75% of the maximum image height,the middle part shows the lateral aberration at the axial image point,and the lower part shows the lateral aberration at an image point of−75% of the maximum image height. In each lateral aberration diagram,the horizontal axis indicates the distance from the principal ray on thepupil surface, and the solid line, the short dash line and the long dashline indicate the characteristics to the d-line, the F-line and theC-line, respectively. In each lateral aberration diagram, the meridionalplane is adopted as the plane containing the optical axis of the firstlens unit G1 and the optical axis of the third lens unit G3.

Here, in the zoom lens system according to each example, the amount ofmovement of the third lens unit G3 in a direction perpendicular to theoptical axis in an image blur compensation state at a telephoto limit isas follows.

Example 1 0.099 mm Example 2 0.097 mm Example 3 0.120 mm Example 4 0.119mm Example 5 0.105 mm Example 6 0.118 mm

Here, when the shooting distance is infinity, at a telephoto limit, theamount of image decentering in a case that the zoom lens system inclinesby 0.3° is equal to the amount of image decentering in a case that theentire third lens unit G3 displaces in parallel by each of theabove-mentioned values in a direction perpendicular to the optical axis.

As seen from the lateral aberration diagrams, satisfactory symmetry isobtained in the lateral aberration at the axial image point. Further,when the lateral aberration at the +75% image point and the lateralaberration at the −75% image point are compared with each other in abasic state, all have a small degree of curvature and almost the sameinclination in the aberration curve. Thus, decentering coma aberrationand decentering astigmatism are small. This indicates that sufficientimaging performance is obtained even in an image blur compensationstate. Further, when the image blur compensation angle of a zoom lenssystem is the same, the amount of parallel translation required forimage blur compensation decreases with decreasing focal length of theentire zoom lens system. Thus, at arbitrary zoom positions, sufficientimage blur compensation can be performed for image blur compensationangles up to 0.3° without degrading the imaging characteristics.

Numerical Example 1

The zoom lens system of Numerical Example 1 corresponds to Embodiment 1shown in FIG. 1. Table 1 shows the surface data of the zoom lens systemof Numerical Example 1. Table 2 shows the aspherical data. Table 3 showsvarious data.

TABLE 1 (Surface data) Surface number r d nd vd Object surface ∞  129.07890 0.65000 1.84666 23.8  2 19.24330 0.01000 1.56732 42.8  319.24330 2.11300 1.49700 81.6  4 86.42200 0.15000  5 25.67730 1.634001.77250 49.6  6 106.76530 Variable  7* 42.46710 0.30000 1.84973 40.6  8*5.21720 3.24100  9* −15.26730 0.40000 1.77200 50.0 10 76.30670 0.1500011 17.04900 1.17960 1.94595 18.0 12 −151.66660 Variable 13(Diaphragm) ∞0.40000 14* 5.01370 2.06080 1.51776 69.9 15* −14.83380 0.31080 167.54190 1.08750 1.69680 55.5 17 −62.32080 0.01000 1.56732 42.8 18−62.32080 0.30000 1.68400 31.3 19* 3.92740 Variable 20* 23.41990 0.500001.68400 31.3 21 13.08220 Variable 22* 16.98930 1.65270 1.58332 59.1 23*−26.72840 Variable 24 ∞ 0.78000 1.51680 64.2 25 ∞ (BF) Image surface ∞

TABLE 2 (Aspherical data) Surface No. 7 K = 0.00000E+00, A4 =−9.72329E−04, A6 = 6.36526E−05, A8 = −1.99584E−06 A10 = 2.92580E−08, A12= −1.63083E−10, A14 = 0.00000E+00 Surface No. 8 K = 0.00000E+00, A4 =−1.22093E−03, A6 = 2.19405E−05, A8 = 1.40953E−06 A10 = −3.56942E−08, A12= −2.36435E−09, A14 = 0.00000E+00 Surface No. 9 K = 0.00000E+00, A4 =5.93781E−05, A6 = −2.69846E−06, A8 = 3.46597E−07 A10 = −6.62230E−09, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 14 K = 0.00000E+00, A4 =−7.54870E−04, A6 = −1.40572E−05, A8 = −1.04531E−05 A10 = 2.38177E−06,A12 = −2.87275E−07, A14 = 1.38097E−08 Surface No. 15 K = 0.00000E+00, A4= 5.09922E−04, A6 = −5.84241E−05, A8 = 5.40285E−06 A10 = −2.75892E−07,A12 = −1.85138E−08, A14 = 3.34187E−09 Surface No. 19 K = 0.00000E+00, A4= 4.20574E−04, A6 = 8.24211E−05, A8 = −7.95809E−07 A10 = −2.57510E−07,A12 = 0.00000E+00, A14 = 0.00000E+00 Surface No. 20 K = 0.00000E+00, A4= −2.19857E−04, A6 = 3.63458E−06, A8 = 4.00573E−07 A10 = −2.82320E−08,A12 = 0.00000E+00, A14 = 0.00000E+00 Surface No. 22 K = 0.00000E+00, A4= 1.05194E−03, A6 = −7.57016E−05, A8 = 5.38661E−06 A10 = −1.94121E−07,A12 = 3.02762E−09, A14 = 0.00000E+00 Surface No. 23 K = 0.00000E+00, A4= 1.08119E−03, A6 = −8.90636E−05, A8 = 5.62747E−06 A10 = −1.80010E−07,A12 = 2.44837E−09, A14 = 0.00000E+00

TABLE 3 (Various data) Zooming ratio 9.39629 Wide-angle Middle Telephotolimit position limit Focal length 4.6443 14.2342 43.6394 F-number3.22092 4.84786 6.12992 View angle 42.0584 15.0863 5.0098 Image height3.6500 3.9020 3.9020 Overall length 42.9083 47.1490 56.1347 of lenssystem BF 0.78233 0.75528 0.75942 d6 0.3000 7.7704 17.9496 d12 16.11825.8225 0.4933 d19 1.5052 8.5986 12.7301 d21 2.2602 3.0078 4.6579 d235.0130 4.2650 2.6150 Entrance pupil 10.7315 24.1995 65.6340 positionExit pupil −15.8295 −42.6408 −164.1662 position Front principal 14.077433.7648 97.7264 points position Back principal 38.2640 32.9148 12.4953points position Single lens data Lens Initial surface Focal elementnumber length 1 1 −69.2960 2 3 49.2954 3 5 43.3837 4 7 −7.0258 5 9−16.4479 6 11 16.2572 7 14 7.5031 8 16 9.7173 9 18 −5.3915 10 20−44.1980 11 22 18.0582 Zoom lens unit data Overall Front Back lengthprincipal principal Lens Initial Focal of lens points points unitsurface No. length unit position position 1 1 35.71662 4.55700 0.753242.45072 2 7 −7.37411 5.27060 −0.04845 0.62571 3 13 10.35837 4.16910−1.69622 0.50121 4 20 −44.19800 0.50000 0.68613 0.88327 5 22 18.058241.65270 0.41137 1.00551 Magnification of zoom lens unit Lens InitialWide-angle Middle Telephoto unit surface No. limit position limit 1 10.00000 0.00000 0.00000 2 7 −0.28379 −0.39829 −0.88471 3 13 −0.56992−1.18735 −1.48366 4 20 1.30781 1.28135 1.24307 5 22 0.61476 0.657680.74882

Numerical Example 2

The zoom lens system of Numerical Example 2 corresponds to Embodiment 2shown in FIG. 4. Table 4 shows the surface data of the zoom lens systemof Numerical Example 2. Table 5 shows the aspherical data. Table 6 showsvarious data.

TABLE 4 (Surface data) Surface number r d nd vd Object surface ∞  118.14520 0.65000 1.84666 23.8  2 13.33980 0.01000 1.56732 42.8  313.33980 3.26860 1.58332 59.1  4* −589.95180 Variable  5* 87.440400.30000 1.84973 40.6  6* 5.37010 2.99770  7* −26.69530 0.40000 1.7720050.0  8 28.62040 0.15000  9 12.92880 1.20490 1.94595 18.0 10 77.42510Variable 11(Diaphragm) ∞ 0.40000 12* 4.78090 1.97140 1.51776 69.9 13*−21.67480 0.38050 14 8.27620 1.04910 1.69680 55.5 15 −36.81240 0.010001.56732 42.8 16 −36.81240 0.30000 1.68400 31.3 17* 4.49740 Variable 18*38.62140 0.50000 1.68400 31.3 19 19.55510 Variable 20* 28.67580 1.355301.58332 59.1 21* −20.57080 Variable 22 ∞ 0.78000 1.51680 64.2 23 ∞ (BF)Image surface ∞

TABLE 5 (Aspherical data) Surface No. 4 K = 0.00000E+00, A4 =7.09435E−06, A6 = 1.39413E−08, A8 = −3.55887E−10 A10 = 1.79420E−12, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 5 K = 0.00000E+00, A4 =−9.04835E−04, A6 = 6.38967E−05, A8 = −1.99616E−06 A10 = 2.89852E−08, A12= −1.62345E−10, A14 = 0.00000E+00 Surface No. 6 K = 0.00000E+00, A4 =−1.12009E−03, A6 = 1.90764E−05, A8 = 2.12713E−06 A10 = −6.28475E−08, A12= −1.45269E−09, A14 = 0.00000E+00 Surface No. 7 K = 0.00000E+00, A4 =3.91664E−05, A6 = −3.88322E−06, A8 = 4.36023E−07 A10 = −6.37301E−09, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 12 K = 0.00000E+00, A4 =−4.60614E−04, A6 = −1.66676E−05, A8 = −6.31506E−06 A10 = 2.29012E−06,A12 = −2.84467E−07, A14 = 1.58823E−08 Surface No. 13 K = 0.00000E+00, A4= 2.37830E−04, A6 = −2.99392E−05, A8 = 1.26348E−05 A10 = −1.02151E−06,A12 = 6.60245E−08, A14 = 1.78751E−09 Surface No. 17 K = 0.00000E+00, A4= 1.55075E−03, A6 = 1.22167E−04, A8 = −6.78885E−06 A10 = 9.45007E−07,A12 = 0.00000E+00, A14 = 0.00000E+00 Surface No. 18 K = 0.00000E+00, A4= −2.46048E−04, A6 = 1.29409E−05, A8 = 2.04153E−08 A10 = −1.93577E−08,A12 = 0.00000E+00, A14 = 0.00000E+00 Surface No. 20 K = 0.00000E+00, A4= 1.37841E−03, A6 = −8.95310E−05, A8 = 5.88917E−06 A10 = −2.03229E−07,A12 = 2.85975E−09, A14 = 0.00000E+00 Surface No. 21 K = 0.00000E+00, A4= 1.41685E−03, A6 = −9.96748E−05, A8 = 6.44922E−06 A10 = −2.09304E−07,A12 = 2.51268E−09, A14 = 0.00000E+00

TABLE 6 (Various data) Zooming ratio 9.39396 Wide-angle Middle Telephotolimit position limit Focal length 4.6471 14.2377 43.6544 F-number3.20754 4.74466 6.12716 View angle 42.4452 15.0755 5.0085 Image height3.6500 3.9020 3.9020 Overall length 41.9901 45.2884 54.5886 of lenssystem BF 0.79321 0.77325 0.75869 d4 0.3000 7.4082 17.3332 d10 16.28595.5822 0.6079 d17 1.5000 8.4137 12.7778 d19 2.3798 2.4889 4.8495 d215.0037 4.8946 2.5340 Entrance pupil 10.5237 23.3494 63.6707 positionExit pupil −15.6608 −35.0905 −111.1803 position Front principal 13.858331.9349 90.3006 points position Back principal 37.3430 31.0506 10.9342points position Single lens data Lens Initial surface Focal elementnumber length 1 1 −63.4272 2 3 22.4078 3 5 −6.7446 4 7 −17.8353 5 916.2597 6 12 7.7625 7 14 9.7908 8 16 −5.8421 9 18 −58.5351 10 20 20.7448Zoom lens unit data Initial Overall Lens surface Focal length of Frontprincipal Back principal unit No. length lens unit points positionpoints position 1 1 35.51130 3.92860 −0.16091 1.34227 2 5 −7.230135.05260 −0.02336 0.75890 3 11 10.19153 4.11100 −1.46087 0.56501 4 18−58.53509 0.50000 0.60791 0.80780 5 20 20.74481 1.35530 0.50354 0.99408Magnification of zoom lens unit Lens Initial Wide-angle Middle Telephotounit surface No. limit position limit 1 1 0.00000 0.00000 0.00000 2 5−0.28445 −0.39487 −0.86227 3 11 −0.55955 −1.22662 −1.51803 4 18 1.212041.20915 1.17530 5 20 0.67836 0.68458 0.79908

Numerical Example 3

The zoom lens system of Numerical Example 3 corresponds to Embodiment 3shown in FIG. 7. Table 7 shows the surface data of the zoom lens systemof Numerical Example 3. Table 8 shows the aspherical data. Table 9 showsvarious data.

TABLE 7 (Surface data) Surface number r d nd vd Object surface ∞  157.34670 0.75000 1.84666 23.8  2 30.67210 0.01000 1.56732 42.8  330.67210 2.81960 1.49700 81.6  4 −136.79070 0.15000  5 23.79550 1.869301.72916 54.7  6 58.21050 Variable  7* 33.55860 0.30000 1.85135 40.1  8*5.35170 3.43870  9 −10.82510 0.30000 1.71300 53.9 10 34.17370 0.16990 1115.57610 1.26730 1.94595 18.0 12 −503.66630 Variable 13(Diaphragm) ∞Variable 14* 5.26740 3.19670 1.52501 70.3 15* −10.92320 0.30000 16−50.00000 0.83700 1.69680 55.5 17 −11.86390 0.01000 1.56732 42.8 18−11.86390 0.40000 1.68400 31.3 19* 15.91570 Variable 20 121.626800.50000 1.68400 31.3 21* 11.25930 Variable 22* 10.78660 2.26080 1.5250170.3 23* −35.76060 Variable 24 ∞ 0.78000 1.51680 64.2 25 ∞ (BF) Imagesurface ∞

TABLE 8 (Aspherical data) Surface No. 7 K = 0.00000E+00, A4 =−8.16586E−05, A6 = 4.93525E−07, A8 = −4.71059E−08 A10 = 6.04514E−10, A12= 0.00000E+00 Surface No. 8 K = 0.00000E+00, A4 = −1.06644E−04, A6 =−1.32278E−05, A8 = 9.85494E−07 A10 = −4.27628E−08, A12 = 0.00000E+00Surface No. 14 K = 0.00000E+00, A4 = −2.98911E−04, A6 = −2.76757E−05, A8= 6.05740E−08 A10 = −2.69111E−07, A12 = 0.00000E+00 Surface No. 15 K =0.00000E+00, A4 = 1.43528E−04, A6 = −5.06916E−05, A8 = −1.94110E−06 A10= 0.00000E+00, A12 = 0.00000E+00 Surface No. 19 K = 0.00000E+00, A4 =1.53349E−03, A6 = 9.73212E−05, A8 = 4.19851E−06 A10 = 1.71434E−08, A12 =0.00000E+00 Surface No. 21 K = 0.00000E+00, A4 = 4.32105E−05, A6 =8.58735E−06, A8 = −1.29261E−06 A10 = 5.75642E−08, A12 = 0.00000E+00Surface No. 22 K = 0.00000E+00, A4 = −6.24838E−04, A6 = 4.67785E−05, A8= −3.02859E−06 A10 = 9.39984E−08, A12 = −1.86680E−09 Surface No. 23 K =0.00000E+00, A4 = −6.58830E−04, A6 = 2.90740E−05, A8 = −9.01156E−07 A10= −8.78842E−09, A12 = 0.00000E+00

TABLE 9 (Various data) Zooming ratio 15.16109 Wide-angle MiddleTelephoto limit position limit Focal length 4.6500 18.6001 70.4998F-number 3.39030 4.68745 6.12369 View angle 42.3265 11.9014 3.1099 Imageheight 3.6000 3.9020 3.9020 Overall length 52.8441 58.5746 69.1106 oflens system BF 0.47960 0.51207 0.46063 d6 0.3000 13.2756 24.3919 d1218.4975 5.6765 1.1483 d13 1.8191 0.3000 0.3000 d19 3.1757 8.3407 11.9271d21 6.4917 3.5318 7.9963 d23 2.7212 7.5786 3.5271 Entrance pupil 11.095440.7684 124.6419 position Exit pupil −61.3743 −44.3322 439.7759 positionFront principal 15.3959 51.6537 206.4552 points position Back principal48.1940 39.9745 −1.3892 points position Single lens data Lens Initialsurface Focal element number length 1 1 −78.9002 2 3 50.6947 3 5 53.96234 7 −7.5156 5 9 −11.4982 6 11 15.9912 7 14 7.2626 8 16 22.1235 9 18−9.8796 10 20 −18.1737 11 22 16.0530 Zoom lens unit data Initial OverallLens surface Focal length of Front principal Back principal unit No.length lens unit points position points position 1 1 39.37702 5.598901.40650 3.47976 2 7 −6.11720 5.47590 0.54923 1.52332 3 14 10.018834.74370 −0.60520 1.29457 4 20 −18.17370 0.50000 0.32781 0.53035 5 2216.05298 2.26080 0.34939 1.10249 Magnification of zoom lens unit LensInitial Wide-angle Middle Telephoto unit surface No. limit positionlimit 1 1 0.00000 0.00000 0.00000 2 7 −0.20194 −0.35327 −0.98672 3 14−0.47714 −1.32117 −1.44572 4 20 1.75980 2.58300 1.93863 5 22 0.696420.39181 0.64740

Numerical Example 4

The zoom lens system of Numerical Example 4 corresponds to Embodiment 4shown in FIG. 10. Table 10 shows the surface data of the zoom lenssystem of Numerical Example 4. Table 11 shows the aspherical data. Table12 shows various data.

TABLE 10 (Surface data) Surface number r d nd vd Object surface ∞  151.53350 0.75000 1.84666 23.8  2 28.69750 0.01000 1.56732 42.8  328.69750 2.62020 1.49700 81.6  4 −167.00710 0.15000  5 23.56150 1.723401.72916 54.7  6 57.34580 Variable  7* 26.00400 0.30000 1.85135 40.1  8*5.07260 3.67090  9 −8.86200 0.30000 1.71300 53.9 10 102.89120 0.15000 1120.30160 1.23410 1.94595 18.0 12 −54.48290 Variable 13(Diaphragm) ∞0.30000 14* 5.10950 3.26090 1.52501 70.3 15* −12.43940 0.36260 16−50.00790 0.99390 1.69680 55.5 17 −9.43060 0.01000 1.56732 42.8 18−9.43060 0.40000 1.68400 31.3 19* 14.51400 Variable 20 213.31420 0.500001.68400 31.3 21* 15.00360 Variable 22* 11.52200 2.05250 1.52501 70.3 23*−42.70170 Variable 24 ∞ 0.78000 1.51680 64.2 25 ∞ (BF) Image surface ∞

TABLE 11 (Aspherical data) Surface No. 7 K = 0.00000E+00, A4 =−1.29016E−04, A6 = 2.90190E−06, A8 = −1.12455E−07 A10 = 1.26618E−09, A12= 0.00000E+00 Surface No. 8 K = 0.00000E+00, A4 = −2.58730E−04, A6 =−1.88614E−05, A8 = 1.55667E−06 A10 = −7.93547E−08, A12 = 0.00000E+00Surface No. 14 K = 0.00000E+00, A4 = −3.22933E−04, A6 = −2.40404E−05, A8= −2.72257E−08 A10 = −1.34244E−07, A12 = 0.00000E+00 Surface No. 15 K =0.00000E+00, A4 = 2.34703E−06, A6 = −2.88793E−05, A8 = −4.99722E−07 A10= 0.00000E+00, A12 = 0.00000E+00 Surface No. 19 K = 0.00000E+00, A4 =1.82516E−03, A6 = 8.73655E−05, A8 = 3.90359E−06 A10 = 4.73697E−08, A12 =0.00000E+00 Surface No. 21 K = 0.00000E+00, A4 = 2.72307E−05, A6 =6.25910E−06, A8 = −5.88975E−07 A10 = 2.38168E−08, A12 = 0.00000E+00Surface No. 22 K = 0.00000E+00, A4 = −6.01980E−04, A6 = 4.78200E−05, A8= −2.82173E−06 A10 = 8.19441E−08, A12 = −1.60425E−09 Surface No. 23 K =0.00000E+00, A4 = −6.54335E−04, A6 = 3.22551E−05, A8 = −1.06168E−06 A10= −5.39506E−09, A12 = 0.00000E+00

TABLE 12 (Various data) Zooming ratio 15.17308 Wide-angle MiddleTelephoto limit position limit Focal length 4.6454 18.6011 70.4851F-number 3.38793 5.02654 6.10042 View angle 42.3892 11.8634 3.1098 Imageheight 3.6000 3.9020 3.9020 Overall length 49.9957 57.8547 68.9731 oflens system BF 0.47349 0.51758 0.46322 d6 0.3000 12.6258 23.5760 d1217.7000 5.4577 0.9788 d19 2.1955 9.9270 14.6285 d21 4.9324 2.9361 7.2490d23 4.8258 6.8220 2.5091 Entrance pupil 10.8136 38.2184 114.5491position Exit pupil −28.7786 −44.4433 1118.4999 position Front principal14.7213 49.1238 189.4779 points position Back principal 45.3503 39.2536−1.5120 points position Single lens data Lens Initial surface Focalelement number length 1 1 −77.6591 2 3 49.4947 3 5 53.6937 4 7 −7.4514 59 −11.4308 6 11 15.7620 7 14 7.3701 8 16 16.5135 9 18 −8.3009 10 20−23.6188 11 22 17.5112 Zoom lens unit data Initial Overall Lens surfaceFocal length of Front principal Back principal unit No. length lens unitpoints position points position 1 1 38.92659 5.25360 1.24863 3.19119 2 7−6.17776 5.65500 0.49349 1.37523 3 13 10.32366 5.32740 −0.66309 1.473574 20 −23.61882 0.50000 0.31970 0.52249 5 22 17.51125 2.05250 0.289770.97860 Magnification of zoom lens unit Lens Initial Wide-angle MiddleTelephoto unit surface No. limit position limit 1 1 0.00000 0.000000.00000 2 7 −0.20666 −0.35167 −0.93363 3 13 −0.55962 −1.45383 −1.66046 420 1.70081 1.90677 1.57931 5 22 0.60668 0.49017 0.73957

Numerical Example 5

The zoom lens system of Numerical Example 5 corresponds to Embodiment 5shown in FIG. 13. Table 13 shows the surface data of the zoom lenssystem of Numerical Example 5. Table 14 shows the aspherical data. Table15 shows various data.

TABLE 13 (Surface data) Surface number r d nd vd Object surface ∞  160.44880 0.75000 1.84666 23.8  2 32.03080 0.01000 1.56732 42.8  332.03080 2.69580 1.49700 81.6  4 −97.40450 0.15000  5 23.51180 1.521401.72916 54.7  6 51.12920 Variable  7* 29.68640 0.30000 1.84973 40.6  8*5.34170 3.77130  9 −8.04110 0.30000 1.71300 53.9 10 −1265.83730 0.1500011 25.77440 1.19890 1.94595 18.0 12 −39.44190 Variable 13(Diaphragm) ∞0.30000 14* 5.08260 3.01780 1.51845 70.0 15 −16.92640 0.37410 1656.25890 1.36760 1.69680 55.5 17 −8.68290 0.01000 1.56732 42.8 18−8.68290 0.40000 1.68400 31.3 19* 12.09960 Variable 20 24.95430 0.500001.84973 40.6 21* 10.33060 Variable 22* 9.80520 2.05250 1.51845 70.0 23*148.40800 2.17600 24 ∞ 0.78000 1.51680 64.2 25 ∞ (BF) Image surface ∞

TABLE 14 (Aspherical data) Surface No. 7 K = 0.00000E+00, A4 =−1.72513E−04, A6 = 6.87473E−06, A8 = −9.75804E−08 A10 = −1.15455E−10,A12 = 0.00000E+00 Surface No. 8 K = 0.00000E+00, A4 = −2.93125E−04, A6 =−1.17933E−05, A8 = 1.18518E−06 A10 = −3.01318E−08, A12 = 0.00000E+00Surface No. 14 K = 0.00000E+00, A4 = −3.63811E−04, A6 = −1.60178E−05, A8= 7.88634E−08 A10 = −4.79116E−08, A12 = 0.00000E+00 Surface No. 19 K =0.00000E+00, A4 = 1.84153E−03, A6 = 7.85211E−05, A8 = 2.94963E−07 A10 =4.92755E−07, A12 = 0.00000E+00 Surface No. 21 K = 0.00000E+00, A4 =5.84721E−06, A6 = 1.04792E−05, A8 = −1.02352E−06 A10 = 3.69061E−08, A12= 0.00000E+00 Surface No. 22 K = 0.00000E+00, A4 = −4.66373E−04, A6 =3.73697E−05, A8 = −2.11059E−06 A10 = 7.56353E−08, A12 = −1.97886E−09Surface No. 23 K = 0.00000E+00, A4 = −8.17898E−04, A6 = 4.11654E−05, A8= −1.45941E−06 A10 = −2.94317E−09, A12 = 0.00000E+00

TABLE 15 (Various data) Zooming ratio 15.16640 Wide-angle MiddleTelephoto limit position limit Focal length 4.6485 18.5973 70.5004F-number 3.38965 5.06465 6.10061 View angle 42.2782 11.6312 3.1412 Imageheight 3.6000 3.9020 3.9020 Overall length 50.5302 55.3093 68.9739 oflens system BF 0.47867 0.51734 0.46373 d6 0.3000 11.6054 23.5100 d1218.9958 5.5910 0.9017 d19 2.4533 10.9617 12.4382 d21 6.4770 4.80859.8349 Entrance pupil 10.7742 33.7420 105.8678 position Exit pupil−28.2436 −42.2486 −264.1589 position Front principal 14.6703 44.2520157.5856 points position Back principal 45.8817 36.7120 −1.5265 pointsposition Single lens data Lens Initial surface Focal element numberlength 1 1 −81.4588 2 3 48.8375 3 5 58.3413 4 7 −7.7093 5 9 −11.3511 611 16.6273 7 14 7.9098 8 16 10.8892 9 18 −7.3333 10 20 −21.0770 11 2220.1486 Zoom lens unit data Initial Overall Lens surface Focal length ofFront principal Back principal unit No. length lens unit points positionpoints position 1 1 39.64625 5.12720 1.38976 3.27251 2 7 −6.163345.72020 0.56057 1.44047 3 13 9.77084 5.46950 −0.59752 1.63155 4 20−21.07697 0.50000 0.46862 0.69400 5 22 20.14859 5.00850 −0.09514 0.87821Magnification of zoom lens unit 1 Lens Initial Wide-angle MiddleTelephoto unit surface No. limit position limit 1 1 0.00000 0.000000.00000 2 7 −0.20032 −0.31668 −0.81551 3 13 −0.48120 −1.28268 −1.62775 420 1.57711 1.50104 1.73524 5 22 0.77125 0.76933 0.77199

Numerical Example 6

The zoom lens system of Numerical Example 6 corresponds to Embodiment 6shown in FIG. 16. Table 16 shows the surface data of the zoom lenssystem of Numerical Example 6. Table 17 shows the aspherical data. Table18 shows various data.

TABLE 16 (Surface data) Surface number r d nd vd Object surface ∞  146.75190 2.65650 1.49700 81.6  2 −58.74640 0.01000 1.56732 42.8  3−58.74640 0.75000 2.00272 19.3  4 −134.86740 0.15000  5 27.19460 1.573001.69680 55.5  6 83.02160 Variable  7* 28.89600 0.30000 1.85135 40.1  8*5.15710 3.78950  9 −7.93880 0.30000 1.71300 53.9 10 −256.72580 0.1500011 27.62940 1.21450 1.94595 18.0 12 −33.20460 Variable 13(Diaphragm) ∞0.30000 14* 4.90800 3.07470 1.52501 70.3 15* −13.24560 0.78790 16−17.78870 1.09340 1.69680 55.5 17 −6.59430 0.01000 1.56732 42.8 18−6.59430 0.40000 1.68400 31.3 19* 22.60770 Variable 20 63.00600 0.500001.68400 31.3 21* 15.88000 Variable 22* 11.66450 1.91960 1.52501 70.3 23*−68.00180 Variable 24 ∞ 0.78000 1.51680 64.2 25 ∞ (BF) Image surface ∞

TABLE 17 (Aspherical data) Surface No. 7 K = 0.00000E+00, A4 =−1.99668E−04, A6 = 8.31248E−06, A8 = −1.61821E−07 A10 = 9.42854E−10, A12= 0.00000E+00 Surface No. 8 K = 0.00000E+00, A4 = −3.69464E−04, A6 =−1.94870E−05, A8 = 1.80882E−06 A10 = −6.49892E−08, A12 = 0.00000E+00Surface No. 14 K = 0.00000E+00, A4 = −2.42537E−04, A6 = −1.73202E−05, A8= 1.99941E−07 A10 = −5.74143E−08, A12 = 0.00000E+00 Surface No. 15 K =0.00000E+00, A4 = 3.53310E−04, A6 = −2.15028E−05, A8 = 6.83562E−07 A10 =0.00000E+00, A12 = 0.00000E+00 Surface No. 19 K = 0.00000E+00, A4 =1.76798E−03, A6 = 1.01479E−04, A8 = −2.20701E−08 A10 = 5.30247E−07, A12= 0.00000E+00 Surface No. 21 K = 0.00000E+00, A4 = −3.44609E−06, A6 =3.37595E−06, A8 = −1.52317E−08 A10 = −1.18245E−09, A12 = 0.00000E+00Surface No. 22 K = 0.00000E+00, A4 = −5.97461E−04, A6 = 2.82900E−05, A8= −1.54049E−06 A10 = 2.96146E−08, A12 = −7.59166E−10 Surface No. 23 K =0.00000E+00, A4 = −6.67729E−04, A6 = 2.20877E−05, A8 = −9.57433E−07 A10= −3.56583E−09, A12 = 0.00000E+00

TABLE 18 (Various data) Zooming ratio 15.16103 Wide-angle MiddleTelephoto limit position limit Focal length 4.6500 18.5999 70.4984F-number 3.39068 4.71336 6.10116 View angle 42.3492 11.9249 3.1092 Imageheight 3.6000 3.9020 3.9020 Overall length 49.6088 57.0332 68.9781 oflens system BF 0.49473 0.51212 0.46799 d6 0.3000 11.5490 22.2968 d1217.6999 5.1424 0.8542 d19 1.4677 10.1832 15.7126 d21 5.5904 2.57717.3873 d23 4.2970 7.3103 2.5001 Entrance pupil 10.7539 34.9443 105.3609position Exit pupil −27.8954 −43.7550 989.4102 position Front principal14.6422 45.7290 180.8849 points position Back principal 44.9589 38.4333−1.5203 points position Single lens data Lens Initial surface Focalelement number length 1 1 52.8235 2 3 −104.3159 3 5 57.3751 4 7 −7.41665 9 −11.4954 6 11 16.0988 7 14 7.2434 8 16 14.4585 9 18 −7.4224 10 20−31.1739 11 22 19.1234 Zoom lens unit data Initial Overall Lens surfaceFocal length of Front principal Back principal unit No. length lens unitpoints position points position 1 1 37.58433 5.13950 1.24965 3.14016 2 7−6.16937 5.75400 0.46007 1.28009 3 13 10.48749 5.66600 −1.07855 1.220014 20 −31.17392 0.50000 0.39868 0.60048 5 22 19.12344 1.91960 0.185840.83617 Magnification of zoom lens unit Lens Initial Wide-angle MiddleTelephoto unit surface No. limit position limit 1 1 0.00000 0.000000.00000 2 7 −0.21529 −0.35443 −0.92651 3 13 −0.57925 −1.63708 −1.85705 420 1.48987 1.68094 1.43210 5 22 0.66589 0.50741 0.76125

The following Table 19 shows the corresponding values to the individualconditions in the zoom lens systems of the numerical examples.

TABLE 19 (Corresponding values to conditions) Example Condition 1 2 3 45 6 (1-2) f_(G1)/Ir 9.34 9.28 10.28 10.17 10.25 9.81 (a) f_(T)/f_(W)9.40 9.39 15.16 15.17 15.17 15.16 (2) (L_(12T) − L_(12W)) × 43.08 41.3364.66 61.79 61.47 56.38 f_(G1)/Ir² (3) f_(G3)/D_(G3) 2.75 2.75 2.11 2.051.89 1.95 (4) f_(G1)/f_(G4) −0.81 −0.61 −2.17 −1.65 −1.88 −1.21 (5)f_(G1)/f_(W) 7.69 7.64 8.47 8.38 8.53 8.08 (6) L_(T)/f_(G3) 5.42 5.366.90 6.68 7.06 6.58

The zoom lens system according to the present invention is applicable toa digital input device such as a digital camera, a mobile telephone, aPDA (Personal Digital Assistance), a surveillance camera in asurveillance system, a Web camera or a vehicle-mounted camera. Inparticular, the zoom lens system according to the present invention issuitable for a photographing optical system where high image quality isrequired like in a digital camera.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless otherwise such changes andmodification depart from the scope of the present invention, they shouldbe construed as being included therein.

1. A zoom lens system, in order from an object side to an image side,comprising a first lens unit having positive optical power, a secondlens unit having negative optical power, a third lens unit havingpositive optical power, a fourth lens unit having negative opticalpower, and a fifth lens unit having positive optical power, wherein thethird lens unit includes at least one lens element having positiveoptical power and at least one lens element having negative opticalpower, in zooming from a wide-angle limit to a telephoto limit at thetime of image taking, at least the first lens unit, the second lensunit, and the third lens unit are individually moved along an opticalaxis so that air spaces between the respective lens units vary, therebyperforming magnification change, in focusing from an infinity in-focuscondition to a close-object in-focus condition, a lens unit positionedon the image side relative to an aperture diaphragm is moved along theoptical axis, and the following conditions (1-2) and (a) are satisfied:8.1<f_(G1)/Ir<10.4  (1-2)Z=f _(T) /f _(W)≧9.0  (a) where f_(G1) is a composite focal length ofthe first lens unit, Ir is a value represented by the followingequation:Ir=f _(T)×tan (ω_(T)), ω_(T) is a half view angle (°) at a telephotolimit, f_(T) is a focal length of the entire system at a telephotolimit, and f_(W) is a focal length of the entire system at a wide-anglelimit.
 2. The zoom lens system as claimed in claim 1, wherein thefollowing condition (2) is satisfied:28.8<(L_(12T)−L_(12W))×f_(G1)/Ir²<70.0  (2) where L_(12T) is an intervalbetween the first lens unit and the second lens unit at a telephotolimit, L_(12W) is an interval between the first lens unit and the secondlens unit at a wide-angle limit, f_(G1) is a composite focal length ofthe first lens unit, Ir is a value represented by the followingequation:Ir=f _(T)×tan (ω_(T)), ω_(T) is a half view angle (°) at a telephotolimit, and f_(T) is a focal length of the entire system at a telephotolimit.
 3. The zoom lens system as claimed in claim 1, wherein thefollowing condition (3) is satisfied:1.85<f_(G3)/D_(G3)<4.29  (3) where f_(G3) is a composite focal length ofthe third lens unit, and D_(G3) is an optical axial thickness of thethird lens unit.
 4. The zoom lens system as claimed in claim 1, whereinthe following condition (4) is satisfied:−4.2<f_(G1)/f_(G4)<−0.5  (4) where f_(G1) is a composite focal length ofthe first lens unit, and f_(G4) is a composite focal length of thefourth lens unit.
 5. The zoom lens system as claimed in claim 1, whereinthe following condition (5) is satisfied:6.0<f_(G1)/f_(W)<9.4  (5) where f_(G1) is a composite focal length ofthe first lens unit, and f_(W) is a focal length of the entire system ata wide-angle limit.
 6. The zoom lens system as claimed in claim 1,wherein the following condition (6) is satisfied:4.3<L_(T)/f_(G3)<7.4  (6) where L_(T) is an overall length of lenssystem at a telephoto limit (a distance from the most object sidesurface of the first lens unit to the image surface), and f_(G3) is acomposite focal length of the third lens unit.
 7. The zoom lens systemas claimed in claim 1, wherein the fourth lens unit is composed of onelens element.
 8. The zoom lens system as claimed in claim 1, wherein thefifth lens unit is composed of one lens element.
 9. The zoom lens systemas claimed in claim 1, wherein the fourth lens unit is moved along theoptical axis in focusing from an infinity in-focus condition to aclose-object in-focus condition.
 10. An imaging device capable ofoutputting an optical image of an object as an electric image signal,comprising: a zoom lens system that forms an optical image of theobject; and an image sensor that converts the optical image formed bythe zoom lens system into the electric image signal, wherein the zoomlens system is a zoom lens system as claimed in claim
 1. 11. A camerafor converting an optical image of an object into an electric imagesignal and then performing at least one of displaying and storing of theconverted image signal, comprising: an imaging device including a zoomlens system that forms the optical image of the object and an imagesensor that converts the optical image formed by the zoom lens systeminto the electric image signal, wherein the zoom lens system is a zoomlens system as claimed in claim 1.